Dependable Arch Sky

Latin dē-pendere, to hang from — adjectival suffix -able. As a color modifier, dependable implies a clear-and-trustworthy-and-consistent quality where the hue carries the visual register of consistently-performing-and-counted-on design-element. Sits at the crisp-and-honest end of the grid, parallel to reliable and trustworthy in usage.

Latin arcus, bow / curve. As a color modifier, arch implies a Roman-and-Gothic-and-Romanesque-vault quality, the visual register of Roman-aqueduct-and-Romanesque-cathedral hand-cut stone-and-brick voussoir-and-keystone arch-and-vault architectural surfaces under monumental architecture light. Sits at the modifier-and-architecture end of the grid, parallel to dome and vault in usage.

The blue of a clear sky at noon — produced by Rayleigh scattering, the preferential dispersion of shorter wavelengths through atmospheric molecules. Air itself is colorless; the color we see is sunlight scattered toward our eyes by every cubic kilometer above. The reference shade is mid-latitude noon under a high pressure system: a clean, slightly green-shifted blue with the luminous depth of light scattered across an entire hemisphere of air.